Can you compare Fluent NHibernate with xml configuration mapping files?

What should I take into consideration if I need to choose between Fluent NHibernate and standa开发者_如何转开发rd xml mapping files of NHibernate?

Can you compare the prominent differences that I should be aware of?

---

Several things and as mentioned this is possibly a duplicate question the main one I can think of is that you can change xml files without a code recompile but you cannot change mappings in fluent without recompiling something because they are by their nature compiled.

That said you can have a mappings assembly and then just patch that. Obviously whatever changes you make then need to be run through integration tests.

Aside from that Fluent Nhibernate can be confusing to NHibernate users because they mix some terms with their own so I always say you should start with XML file mappings until you totally understand whats going on then migrate to Fluent if you don't need to change the mappings without recompilation as it just reads better.

However don't forget you are then adding a layer of abstraction over the top with its own quirks which can make for interesting debugging.

---

Note: This is more of an opinion answer.

There's actually a 3rd option which you missed. NHibernate 3.2 shipped with it's own code mapping syntax.

http://nhforge.org/blogs/nhibernate/archive/2011/09/05/using-nh3-2-mapping-by-code-for-automatic-mapping.aspx

Personally I don't like the syntax, I'm a Fluent NHibernate fan and it works for me.

I think the only real thing to consider is what krystan already mentioned, which is the naming differences.

I personally threw in the towel with the XML mappings, and didn't pick NHibernate up again until Fluent NHibernate came out.

I don't believe you need to know anything about XML mappings, if you want to learn the XML mappings you can export Fluent mappings and look at them. But really the Fluent Mappings are dead simple.

Most problems from Fluent NHibernate steam from attempting to use Auto Mapping which maps a lot of assumptions, it's fine if you're planning on generating the DB schema, but if you've got an existing schema it's best to explicitly map them. I always explicitly write my maps tho.